LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


GIFT    OF 


Class 


V 


By    Starlight 
\  and  Moonlight 

With  the  Warner  &  Svvasey 

Prism 
Terrestrial    Telescope 


The  Warner   &   Suasey    C 


CLEVELAND 


Price  25  cents 


BY  STARLIGHT 
and  MOONLIGHT 


With  the  Warner  &  Swasey 
Prism  Terrestrial 
Telescope 


Some  Easy  Astronomical 
Observations 


• 


The  Warner  &  Swasey  Company 

CLEVELAND,  OHIO 


Copyright,  1909,  by  The  Warner  &>  Swasey  Co. 
Cleveland,  Ohio 


"//  adds  a  precious  seeing  to  the  eye,"1 

—Shakespeare  ;  Love  s  Labour  s  Lost. 


194838 


THE  WARNER  &  SWASEY  PRISM    TERRESTRIAL  TELESCOPE 

Complete    with 

ALT-AZIMUTH  MOUNTING,  FOLDING  TRIPOD 
AND  CARRYING  CASE 


OF  THE 

UNIVERSITY 

OF 


The   Warner    C&>    Swasey    Prism 
Terrestrial  Telescope 

This  Porro  Prism  instrument  represents  the 
highest  development  in  Terrestrial  Telescopes. 
Its  relation  to  the  ordinary  telescope  is  the  same 
as  that  of  our  Prism  Binocular  to  the  old  type  of 
field-glass.  It  is  remarkable  for  its  large  field, 
brilliant  illumination  and  clear  definition. 

The  objective  is  2  inches  in  diameter,  clear  aperture.  Two 
eye-pieces  are  provided,  magnifying  respectively  25  and  50  diam- 
eters. The  telescope  tube  and  the  alt-azimuth  mounting  are  made  of 
aluminum.  The  folding  tripod  is  of  carefully  selected  ash.  All  are 
contained  in  a  neat  leather-covered  carrying  case;  total  weight 
only  twelve  pounds.  Weight  of  telescope  with  its  tripod  and 
mounting,  apart  from  case,  but  six  and  a  half  pounds. 

The  high  quality  of  its  optical  equipment,  and  the  simplicity 
and  adequacy  of  its  mechanical  provisions,  make  it  superior  to  any 
similar  telescope  upon  the  market  for  the  camper,  the  traveler,  the 
motor-tourist,  the  surveyor,  or  the  marksman  upon  the  rifle-range. 
It  is  especially  adapted  for  porch,  seaside  and  general  use. 

While  thus  designed  strictly  as  a  terrestrial  telescope,  its 
purchasers  have  also  found  it  of  much  interest  and  value  in  the 
field  of  amateur  astronomy.  It  is  not  presented  as — in  the  tech- 
nical sense — an  astronomical  telescope;  and  yet  its  quality  is  so 
superior  that  its  efficiency  is  actually  greater  than  that  of  many 
larger  astronomical  telescopes  heretofore  offered  to  the  public. 
The  ease  with  which  it  can  be  moved  from  place  to  place  in  the 
observation  of  moon  and  stars,  its  sharp  definition  and  breadth  of 
field,  combined  with  the  precision  and  steadiness  with  which  the 
instrument  may  be  "pointed"  and  controlled,  have  brought  many 
expressions  of  satisfaction  from  those  who  having  first  purchased 
it  as  a  terrestrial  telescope  have  subsequently  tested  it  in  their 
observations  of  celestial  objects.  To  respond  to  the  interest  and 
the  demand  thus  indicated,  and  to  illustrate,  for  beginners,  some 
of  the  simple  astronomical  uses  of  the  Warner  &  Swasey  "Prism 
Terrestrial,"  this  little  booklet  has  been  prepared. 

Our  long  experience  in  making  "Optik  Tubes"  of  all  sizes, 
from  the  great  Lick  and  Yerkes  Telescopes  to  the  Telescopic  Gun 
Sights,  Range  Finders,  Sextants,  etc.,  used  by  the  Army  and  Navy, 
especially  qualifies  us  to  develop  from  both  a  scientific  and  prac- 
tical standpoint,  the  highest  type  of  Porro  Prism  Telescope. 


By  Starlight  and  Moonlight 

WITH   THE   WARNER    C&    SWASEY 
PRISM     TERRESTRIAL     TELESCOPE 


Introductory 

The  beginner  naturally  asks,  "What  is  there  to  see?  What 
objects  in  the  sky  will  my  telescope  reveal?"  It  will  help  toward 
an  appreciation  of  what  his  little  instrument  will  do  for  him,  if 
we  can  first  help  him  to  understand  some  of  the  things  which  even 
the  largest  telescope — in  direct  proportion  to  its  excellence — will 
not  do  for  anyone. 

There  are  results  which  are  mathematically  as  impossible  for 
an  optical  instrument  as  for  a  fine  watch  to  tick  seventy-five  sec- 
onds to  the  minute.  Your  telescope  cannot  work  well  through  a 
misty  atmosphere,  or  through  air  heavy  with  cloudiness  or  smoke. 
It  will  not  work  well  if  you  permit  the  steadiness  of  your  tripod 
to  be  affected  by  the  winds,  or  if — when  you  place  it  on  your 
porch — the  floor  on  which  it  rests  is  shaken  by  heavy  walking. 
Inasmuch  as  the  atmosphere  close  to  the  earth  is  more  subject  to 
disturbance  and  impurity  than  the  air  a  little  higher  up,  your  in- 
strument will  work  better  on  objects  at  a  slight  altitude  than  on 
objects  lying  close  to  the  horizon. 

Yet  even  this  two-inch  instrument  (modest  indeed  as  com- 
pared to  those  largest  telescopes  of  the  world — the  great  instru- 
ments made  by  The  Warner  &  Swasey  Company  for  the  Lick  and 
the  Yerkes  Observatories)  will  give  you  gratifying  results.  There 
is  a  peculiar  fascination  in  being  easily  able  to  point  your  instru- 
ment at  a  bright  star  and  to  find — perhaps  to  your  surprise — that 
it  is  not  a  single  star,  but  a  "double"  or  a  "triple."  It  is  even  more 
charming  to  be  able  to  discern  in  a  double  star  the  contrasted  colors 
of  the  components, — one,  perhaps,  being  a  golden  yellow,  the  other 
a  distinct  blue  or  a  delicate  emerald. 

A  few  of  the  coarser  doubles  may  be  divided  by  a  field-glass, 
but  everyone  knows  the  difficulty  in  holding  a  field-glass  steady; 
and  the  power  commanded  by  this  little  telescope  is  so  much 
greater  than  that  available  in  a  binocular  that  many  doubles  which 


no  field-glass  can  divide  will  yield  instantly  to  its  persuasion.  And 
as  your  tripod  does  the  holding,  you  can  gaze  at  your  leisure  and 
comfort  into  a  steady  field. 

When  Halley's  comet  comes  again  into  view  (it  is  scheduled  to 
reappear  late  in  1909,  becoming  still  more  conspicuous  in  1910)  the 
possession  of  an  adequate  telescope,  even  though  a  small  one,  will 
add  much  to  one's  pleasure  in  following  its  course.  Objects,  more- 
over, that  are  quite  familiar  to  us — such  a  star-cluster  for  example 
as  the  Pleiades — assume  through  this  little  instrument  a  scope  and 
brilliancy  quite  unsuspected  by  the  naked  eye.  Clusters,  also,  like 
those  in  the  sword-hand  of  Perseus  and  like  the  "Bee-hive"  in 
Cancer;  nebulae  like  those  in  Andromeda  and  Orion;  the  four 
greater  satellites  of  Jupiter;  the  ring-formation  and  at  least  one 
of  the  satellites  of  Saturn,  and  much  of  the  strange  and  beautiful 
topography  of  our  own  moon — are  brought  within  the  range  of 
vivid  interest  and  appreciation.  A  telescope  that  will  easily  divide 
such  double  stars  as  Castor,  and  the  Gamma  in  Virgo;  that  will 
reveal  so  clearly  the  contrasted  colors  of  such  doubles  as  Mizar 
and  Albireo,  and  that  will  show — even  with  a  power  of  50 — the 
trapezium  in  the  sword  of  Orion,  is  not  to  be  despised  by  anyone, 
and  holds — for  the  beginner — many  possibilities  of  pleasure. 


10 


Part  I. 


Single  Stars        Double  Stars 
The  Planets 


Symbols 
%  First  Magnitude  Stars 

•  •Second  Magnitude 

•  Third  Macjnifudf  and  Under 
O  Cluster 

A  Nebula 


GUIDE  MAP  No.  I. 


This  Map  of  #ie  Northern  Sky  Joins,  and  overlaps  the  tops  of 
Maps  II,  III,  IV. 


On  some  evening  when  the  air  is  clear  and  steady,  place  your 
telescope  on  its  simple  mounting,  and  come  with  it  out  of  doors. 
Bring  with  you,  for  your  greater  comfort  while  observing,  a  plain 
straight-backed  chair,  preferably  without  arms. 

Let  us  face  directly  north, — to  get  our  bearings  by  the  Great 
Dipper  and  the  North  Star.  During  May,  at  9  o'clock  in  the 
evening,  for  example,  you  will  find  the  Dipper  just  before  you, 
directly  to  the  northward  and  very  high  up.  During  July  and 
August,  you  will  see  it  further  to  your  left  in  the  northwest,  the 
handle  following  the  bowl  and  the  bowl  turning  slowly  downward, 
as  its  stars  make  their  apparent  revolution  about  the  pole  of  the 
heavens.  Late  in  the  autumn,  you  will  find  it  low  down,  directly 
to  the  north,  its  bowl  turned  upward;  and  in  the  winter,  you  will 
see  it  climbing  upward  to  your  right,  in  the  northeast,  but  with  its 
bowl  turned  toward  the  west. 

In  noting  this  apparent  revolution  of  the  Dipper,  we  have 
taken  9  P.  M.  as  the  hour  of  observation.  As  it  takes  approxi- 
mately twenty-four  hours  to  complete  its  turning,  we  shall  find  it 
at  8  P.  M.  less  far  advanced  upon  its  course;  at  10  P.  M.  or  at  11 
P.  M.,  we  shall  find  it  proportionately  further  forward.  A  few 
minutes'  observation  for  an  evening  or  two  will  make  these  direc- 
tions clear ;  but  as  many  may  wish  to  study  more  fully  the  motions 
of  the  stars,  and  as  all  ought  to  have  larger  knowledge  of  the  im- 
portant constellations  (an  easy  and  delightful  subject  of  popular 
information)  some  elementary  books  of  reference  are  given  on 
page  37 ;  see  also  paragraph  9,  page  36. 

12 


First  let  us  look  at  Mizar,  the  star  marked  Zeta  (£)  in  the 
bend  of  the  Dipper's  handle.  The  reader  who  is  not  familiar  with 
the  characters  of  the  Greek  alphabet  will  quickly  pick  them  up  as 
we  go  along;  some  of  the  stars  have  no  other  designations. 

Quite  near  to  Mizar  you  will  note,  if  the  air  is  clear,  a  little  star 
that  may  sometimes  be  seen  with  the  naked  eye.  Using  your  25  x 
eye-piece,  turn  your  telescope  upon  them.  Be  sure  to  get  a  clean, 
sharp  focus.  You  will  observe  at  least  four  objects  in  the  field. 
You  will  see  Alcor,  the  smaller  star  to  which  we  have  referred,  and 
another  fainter  star,  and  by  looking  closely  at  Mizar  (the  brightest 
of  the  group),  you  will  discover  that  it  is  a  "double."  Now,  having 
once  found  these  in  your  telescope,  slip  in  the  50  x  eye-piece,  and 
the  division  between  Mizar  and  its  close  companion  will  be  clearer 
still.  (The  magnitudes  of  the  components  are  2.4  and  4.2.) 

Now  let  us  look  somewhat  further  from  the  pole,  near  the  edge 
of  our  little  map,  at  a  star  which  the  Dipper's  handle  (if  it  were 
continued  in  a  curve)  would  quite  enclose.  This  is  Alpha  in  "The 
Hunting  Dogs"  (Canes  Venatici).  It  is  sometimes  called  Cor 
Caroli,  the  Heart  of  Charles,  in  honor  of  Charles  I  of  England. 
Your  25  x  will  show  it  to  be  a  charming  double.  (The  magnitudes 
of  the  components  are  3.1  and  5.7.) 

In  searching  for  a  star  with  the  telescope,  it  is  well  to  use  the 
less  powerful  eye-piece.  Having  found  the  object,  you  can  then 
slip  in  the  higher  power  if  you  desire.  Let  us  now  follow  with  our 
eyes  the  general  direction  indicated  by  the  "Pointers"  in  the  bowl 
of  the  Dipper.  Not  stopping,  however,  at  the  Pole  Star,  let  us 
continue  the  imaginary  line  as  far  again,  right  across  the  northern 
sky.  We  are  now  in  the  neighborhood  of  the  constellations  Cepheus 
and  Cassiopeia.  Almost  at  the  center  of  Cepheus,  we  shall  find 
the  little  star  Xi  (£)  ;  magnitudes  4.4  and  6.5.  You  may  find  it  a 
little  difficult.  Turning,  however,  to  one  of  the  corners  of  the 
house-shaped  figure,  we  shall  find  an  especially  easy  and  very  pretty 
"double"  in  the  star  Delta  (8)  ;  magnitudes  3.7  and  5.1,  and  we 
shall  find  another  in  the  head  of  Draco,  the  Dragon.  From  the 
star  Delta  (8)  in  Cepheus  let  the  eye  project  an  imaginary  line 
to  Alpha  (a)  in  the  same  group  —  continuing  it  approximately 
the  distance  of  the  Dipper's  total  length.  You  will  thus  come 
readily  to  the  stars  that  mark  the  Dragon's  head.  The  star  Nu 
(v)  is  the  faintest  of  the  four ;  but  even  with  your  25  x  eye-piece 
you  will  be  rewarded  by  the  brightness  of  its  two  components, 
(magnitudes  4.9  and  4.9). 

And  now  before  leaving  the  northern  stars  let  us  return  again 
to  the  region  right  across  the  northern  sky  from  the  Great  Dipper. 
Still  using  your  low-power  eye-piece,  sweep  through  the  rich  fields 
of  Cassiopeia  till  you  reach  the  neighborhood  of  the  star  Alpha  (a) 
in  Perseus.  This  is  one  of  the  most  brilliant  sections  of  the  sky. 
Note  especially  the  star-clusters  marked  (X)  and  (h).  They  have 
symbolized  for  ages  "the  sword-hand"  of  the  hero  Perseus.  Of 
course  a  larger  instrument  would  give  a  more  adequate  impression 
of  their  scope  and  splendor,  but  our  little  telescope  will  reveal  much 
of  the  beauty  of  the  scene. 

13 


Joins  Map  X 


GUIDE  MAP   No.  II.         T/i/s  Map  Overlaps  Map  I  at  the  Top  and 
Map  III  and  IV  at  the  Sides. 

We  have  already  spoken  of  the  region  of  the  sky  in  the  neigh- 
borhood of  the  star  Alpha  (a)  in  Perseus.  We  find  Perseus  in 
the  northeast  late  in  August  and  the  early  autumn;  in  the  north- 
west during  February  and  the  early  spring.  At  the  right  side  of 
Map  II  toward  the  top,  you  will  find  this  part  of  the  sky  repeated, 
for  the  tops  of  the  oblong  maps  we  now  employ  are  "overlaps" 
connecting  the  circumpolar  stars  with  the  other  stars  of  the  sky. 
You  will  also  see  the  star  Beta  ((3) — or  Algol,  by  name — and  you 
will  note  that  a  line  drawn  from  Beta  (/?)  to  Alpha  (a)  will  form 
a  right  angle  with  one  drawn  to  the  star  Gamma  (y)  in  Androm- 
eda. The  latter  is  one  of  the  most  charming  of  all  the  double 
stars  (magnitudes  2.2  and  5.0)  ;  the  colors  of  its  components  are 
orange  and  a  delicate  emerald.  It  will  repay  close  observation  with 
both  your  eye-pieces. 

Next  let  us  look  at  the  well-known  group  called  the  Pleiades. 
They  appear  in  the  east  in  the  early  evenings  of  late  September, 
reach  their  highest  point  above  us  early  in  January  and  continue 
till  April  in  the  western  sky.  They  are  so  far  distant  that  their 
light,  traveling  at  the  rate  of  more  than  186,000  miles  a  second, 
takes  more  than  two  hundred  years  to  reach  us.  The  average 
unaided  eye  can  discern  but  six  or  seven ;  turn  your  little  instru- 
ment upon  them — using  your  25  power  eye-piece — and  you  will  see 
the  shining  of  hundreds. 

Now  let  us  turn  our  telescope  upon  the  region  about  Alde- 
baran,  the  red  eye  of  Taurus,  the  Bull.  The  stars  that  here  make 

14 


the  V-shaped  figure  which  we  see  in  our  little  map — the  point  of 
the  V  being  at  the  star  Gamma  (y) — are  called  the  Hyades.  The 
group  is  not  so  compact  as  the  Pleiades,  but  it  is  well  worth  exam- 
ination. Note  especially  the  little  star  Theta  (0)  quite  near 
Aldebaran  (mags.  4.0  and  3.6).  Many  can  divide  it  with  the  un- 
aided eye. 

Early  in  November,  the  stars  of  Orion  begin  to  be  seen  in 
our  eastern  sky.  There  is  no  other  constellation  quite  so  impres- 
sive ;  and  from  November  till  late  in  April,  when  it  sinks  below  the 
western  horizon  in  the  early  evening,  it  is  well-placed  for  easy 
observation.  Here — as  always — begin  with  your  eye-piece  of  low- 
est power.  First  note  the  uppermost  of  the  three  bright  stars  in 
Orion's  belt — the  one  marked  Delta  (8).  It  is  an  easy  "double" 
(mags.  2.4  and  6.8).  Then  turn  to  the  little  star  just  below  and 
to  the  right  of  the  lowest  star  of  the  belt.  We  refer  to  the  un- 
marked star  near  to  Zeta  (£).  It  is  a  "multiple"  star  (Sigma,  <r) 
and  even  with  our  little  instrument  you  can  clearly  discern  at  least 
three  of  the  components  (mags.  5,  6.8,  6.3).  Next  let  us  look  a 
little  lower  still,  at  the  star  Theta  (0).  This  is  a  region  of  be- 
wildering interest.  Here  you  will  clearly  observe — especially  if  the 
moon  be  not  shining  so  bright  as  to  obscure  the  light  of  other 
objects — the  beautiful,  mysterious  halo  of  the  "Great  Nebula  of 
the  heavens."  Almost  at  its  center,  if  you  will  now  use  your  50  x 
eye-piece,  you  will  discern  Theta's  four  components,  for  the  star 
is  a  "quadruple"  (mags.  6.8,  7.9,  5.3,  6.8).  Small  as  they  will 
seem,  you  will  clearly  observe  them  as  separate  points  of  light. 
They  form  an  irregular  square — the  famous  "trapezium" — lying 
close  together  in  a  dark  space  at  the  core  of  the  enfolding  radiance. 

Just  below,  note  the  star  Gamma  (y)  in  Lepus  (mags.  5.6  and 
6.4)  ;  and  to  the  left  of  Orion  note  the  star  marked  8  (mags.  4.6 
and  6.7);  and  that  marked  11  (mags.  4.3  and  5.7).  These  are 
easy  and  pretty  doubles. 

We  have  looked  at  two  of  the  clusters  easily  seen  with  the 
unaided  eye;  now  let  us  look  at  two  which  but  for  the  telescope 
not  so  many  eyes  would  find.  You  will  see  the  place  of  the  first 
of  these,  marked  with  the  little  circle,  just  below  the  bright  star 
Sirius.  A  little  searching  with  your  low-power  eye-piece  will  soon 
be  rewarded  by  the  sparkle  of  its  "star-dust."  The  second  is  shown 
nearer  the  top  of  our  map,  in  the  constellation  Cancer.  Its  name 
is  Praesepe,  "The  Manger."  You  will  find  it  slightly  to  one  side 
of  an  imaginary  line  drawn  from  Castor  to  Pollux  and  projected 
southward.  The  myriad  little  stars  of  the  cluster  seem  so  busy  in 
their  twinkling  that  it  has  often  been  called  "the  Bee-hive." 

Among  the  "doubles"  in  this  quarter  of  the  sky  are  the  star 
Iota  (  i  )  just  above  the  "Bee-hive"  (mags.  4.2  and  6.6)  ;  the  star 
Zeta  (£)  in  Gemini  (mags.  3.7  and  7.0),  and  Castor  itself,  one  of  the 
most  beautiful  of  telescopic  objects  (mags.  1.9  and  2.8).  The  two 
components  form  a  "binary"  system,  being  in  slow  revolution 
about  a  common  center.  The  companion  stars  will  seem  very 
close  together  in  so  small  a  telescope,  but  with  the  50  x  eye-piece 
and  on  a  clear  night,  a  good  eye  will  easily  divide  them. 

15 


Joins  Ma/a  I 


G  VIDE  MAP  No.  HI.         This  Map  Overlaps  Map  I  at  the   Top,  and 
Maps  IV  and  II  at  the  Sides. 


As  with  the  other  oblong  maps,  the  top  of  this  map  joins  Map  I, 
partly  overlapping  it  and  therefore  showing  some  of  the  stars 
that  we  noted  on  p.  12.  Among  these  is  the  pretty  "double" — not 
far  from  the  Dipper's  handle — marked  Alpha  (a)  in  the  constella- 
tion Canes  Venatici.  We  may  now  note  also  the  very  easy  double 
quite  near  it  marked  15;  its  components  being  magnitudes  6.2  and 
6.4.  These  stars  are  shown  here  near  the  upper  border  of  our  map, 
about  midway  between  the  two  sides.  They  come  into  good  posi- 
tion at  the  northeast  about  the  middle  of  February,  and  though 
rather  high  up  in  May,  June  and  July,  they  are  again  well  placed 
for  observation  at  the  northwest  during  the  evenings  of  August  and 
September. 

Just  to  the  south  of  them  you  will  observe  the  pretty  groups 
or  strands  of  stars  called  "Bernice's  Hair."  The  name  does  not 
appear,  but  you  will  see  them  on  our  map  just  to  the  right  of 
Arcturus.  Sweep  through  them  with  your  low-power  eye-piece, 
and  you  will  be  delighted  with  the  spectacle. 

Through  the  early  evenings  of  spring  we  shall  also  find  the 
constellation  Leo  in  our  eastern  sky.  Leo  is  rather  high  up  during 
the  evenings  of  April  and  May,  but  is  again  in  good  position  in  our 
western  skies  during  June  and  July.  You  will  easily  recognize  it 
by  the  "sickle"  formed  from  the  stars  Regulus,  Eta  (77),  Gamma 
(y) ,  etc.  First  using  your  lowest  power,  let  us  look  at  the  star  Gamma 

16 


(y).  You  will  note  quite  near  it  a  little  neighbor-star,  not  its 
double — for  it  is  connected  with  the  larger  star  only  in  the  line  of 
sight — yet  it  presents  a  pleasing  contrast  in  size  and  color.  Now 
change  to  the  highest  power  eye-piece  you  have.  This,  if  you  have 
a  good  eye  and  the  atmospheric  conditions  are  favorable,  will  show 
you  that  Gamma  (y),  the  larger  star,  is  also  a  real  double,  a  binary 
— the  two  components  (mags.  2.6  and  3.8)  being  in  slow  revolution 
about  a  common  center.  With  the  star  Gamma  (y)  in  Virgo  (mags. 
3.6  and  3.6)  you  will  also  need  your  highest  power,  but  as  the  dis- 
tance between  the  components  is  greater,  even  the  beginner — if  the 
night  is  good — will  be  delighted  with  his  success.  With  the  power 
of  50x,  in  our  little  instrument,  it  is  one  of  the  most  charming 
objects  in  the  sky. 

One  of  the  easiest  of  the  "doubles"  among  the  early  evening 
stars  of  the  spring  and  summer  is  Alpha  (a),  mags.  5.3  and  2.9,  in 
the  constellation  Libra.  Libra  rises  in  the  southeast  during  May 
and  continues  in  our  southern  skies  till  it  sets  at  the  southwest  in 
October.  We  may  also  try  the  star  Delta  (8)  in  Corvus,  though  we 
shall  find  this  more  difficult.  Returning  now  to  the  top  of  our  map 
let  us  look — in  the  region  near  Arcturus — at  the  star  Pi  (TT)  in 
Bootes;  mags.  4.6  and  6.0;  and  at  Delta  (8),  mags.  3.5  and  8.2,  in 
the  same  constellation.  Next,  and  to  the  left,  you  will  see  the  stars 
of  Hercules.  While  this  immediate  region  of  the  sky  is  too  di- 
rectly overhead  for  easy  observation  in  the  early  evening  of  August, 
it  is  in  good  position  at  the  east  during  the  early  spring  and  at  the 
west  during  the  early  autumn.  We  shall  need  our  highest  power 
in  looking  at  Alpha  (a)  mags.  3.4  and  5.3,  but  even  with  our 
25  x  eye-piece  we  shall  find  a  pretty  double  in  the  star  Kappa  (K), 
mags.  5.3  and  6.5.  And  now  let  us  follow  the  line  indicated  be- 
tween Eta  (77)  and  Zeta  (£)  till  we  come  to  the  cluster  indicated 
by  the  little  circle  lying  between  them.  It  is  globular  in  form, 
and  in  a  large  instrument  is  most  impressive.  The  elder  Herschel 
estimated  the  presence  within  it  of  14,000  stars. 

Turning  again  to  the  lower  half  of  our  map,  at  the  left,  let  us 
next  note  some  of  the  objects  in  Scorpio.  Rising  at  the  southeast 
in  the  month  of  May  and  continuing  at  the  south  through  the  early 
evenings  till  they  set  in  September  at  the  southwest,  the  stars  of 
this  superb  constellation  are  always  in  fine  position  for  the  observer 
of  our  summer  skies.  Use  first  your  low-power  eye-piece  in  sweep- 
ing through  the  whole  field  of  these  stars.  Then  look — using  each 
eye-piece  in  turn — at  the  double  star  marked  Nu  (v),  magnitudes 
6.4  and  4.2;  and  then  at  Beta  (£),  magnitudes  2.9  and  5.0.  These 
are  easy  to  divide  and  yet  sufficiently  close  to  be  very  interesting 
objects  of  their  class.  Follow,  then,  with  your  low-power  eye-piece 
the  course  of  the  Scorpion's  tail.  You  will  find  the  star  Mu  (//,) 
and  the  region  just  below  it  well  worthy  of  your  study.  The  star 
clusters  of  Scorpio  and  of  Sagittarius  (Map  IV),  some  of  which 
are  marked  in  our  maps  by  the  little  circles,  are  not  brilliant  in  a 
small  telescope,  but  the  finding  of  a  few  of  them  will  add  much  to 
your  appreciation  of  this  region  of  the  sky. 

17 


Joins  Map  I 


GUIDE  MAP  No.  IV.         TMs  Map  Overlaps  Map  TVo.  7  af  the  Top,  and 
Maps  II  and  III  at  the  Sides. 

As  we  begin  with  the  stars  in  Map  IV  let  us  again  turn  for  a 
moment  to  No.  I,  and  note  the  position  of  the  Dipper  in  relation 
to  some  of  the  stars  near  the  lower  border  of  that  map.  As  the 
Dipper  looms  above  us  in  the  evening  skies  of  May  you  will  see, 
low  down  and  to  the  right,  the  stars  of  Lyra  rising  at  the  northeast. 

In  Map  IV,  at  the  top,  you  will  now  observe  the  repetition  of 
some  of  the  objects  of  this  region;  you  will  note  that  Vega,  the 
leading  star  in  Lyra,  is  between  the  constellation  Hercules,  on  the 
one  hand,  and  Cygnus  on  the  other;  and  you  will  see,  further,  that 
all  these  stars  hold  always  the  same  fixed  position  in  reference  to 
the  great  Dipper.  When  the  Dipper  is  high  up  these  are  in  the 
northeast;  as  the  Dipper  sinks  toward  the  west  these  rise  to  the 
meridian ;  as  the  Dipper  itself  wheels  again  into  the  northeast,  they 
sink  below  the  horizon  at  the  northwest.  To  the  beginner  such 
descriptions  (see  also  p.  12  and  par.  9  on  p.  36)  may  sound  a 
little  "complicated,"  yet  if  he  will  look  for  an  evening  or  two  at 
the  actual  skies,  glancing  now  and  then  at  his  little  maps,  he  will 
find  few  things  more  pleasurable  than  "the  simplicity  of  the  stars." 

On  a  clear  night  Vega  can  always  be  identified  by  the  rhomboid 
("the  slanting  oblong  square")  formed  by  the  stars  Delta  (8), 
Gamma  (y),  Beta  (f3),  and  Zeta  (£)•  Of  these,  all  except  the  second 
are  double  stars,  the  first  named  being  the  easiest  to  divide.  The 
components  of  Delta  (8)  are  magnitudes  5.5  and  4.5.  Beta  is  a 
"multiple,"  only  two  of  the  components  being  within  the  range  of 
our  instrument  (magnitudes  3.3  and  6.7).  The  magnitudes  of 

18 


Zeta  (£)  are  4.2  and  5.8.  We  will  now  direct  ourselves  to  the  little 
star  Epsilon  (e).  It  is  a  very  easy  double,  magnitudes  5.0  and  6.0, 
but  of  much  more  interest  is  the  fact  that  each  of  these  components 
is  itself  a  double,  the  two  pairs  being  in  very  slow  revolution  about 
a  common  center.  The  doubling  of  the  doubles  is  beyond  the 
power  of  so  small  an  instrument,  but  the  knowledge  of  a  fact  so 
unique  in  stellar  history  always  gives  a  peculiar  interest  to  them 
as  telescopic  objects. 

Not  far  from  Lyra  we  find  those  stars  of  Cygnus,  the  Swan, 
which  form  the  Northern  Cross.  No  star  in  the  sky  makes  a  more 
beautiful  or  more  satisfactory  object  for  our  telescope  than  "Al- 
bireo,"  marked  as  Beta  ((3)  at  the  foot  of  this  cross.  The  magni- 
tudes are  3.2  and  5.3,  and  the  contrasted  colors — a  golden  yellow 
and  a  smalt  blue — make  an  especially  fine  contrast.  The  star 
Omicron  (o)  is  also  an  easy  double  (magnitudes  4.9  and  3.9),  and 
the  star  marked  61  (magnitudes  5.5  and  6.2)  while  perhaps  requir- 
ing your  50  x  eye-piece  for  its  division,  is  of  interest  as  being  the 
nearest  to  our  earth  of  all  the  stars  in  the  northern  sky.  So  far 
away  is  it,  however,  that  its  light  requires  approximately  eight 
years  in  which  to  reach  us! 

Southward  from  Cygnus  you  will  find  another  beautiful  double 
in  Theta  (6),  magnitudes  4.5  and  5.1,  of  the  constellation  Serpens. 
You  can  find  it  by  extending  an  imaginary  line  from  Eta  (rj)  to 
Delta  (8)  in  Aquila,  and  continuing  it  an  equal  distance.  Still 
further  to  the  southward  you  will  find  a  very  easy  double  in  Alpha 
(a)  of  Capricornus;  many  can  divide  the  components,  magnitudes 
4.5  and  3.7,  with  the  unaided  eye.  A  closer  and  more  interesting 
double  is  Beta  (/3)  of  the  same  constellation,  magnitudes  3.2  and 
6.0;  the  colors  being  an  orange  yellow  and  a  sky  blue. 

The  stars  of  this  region  are  well  placed  for  observation 
throughout  the  summer,  rising  at  the  southeast  in  July  and  con- 
tinuing in  our  evening  skies  till  they  set  in  November  at  the 
southwest.  In  Aquarius  you  will  find  that  Zeta  (£)  the  central  star 
of  the  little  Y  which  marks  the  water-jar  is  a  double,  though  rather 
difficult;  mags.  4.5  and  4.2.  Gamma  (y)  in  the  small  constellation 
called  Delphinus  is  more  easily  divided;  mags.  5.4  and  4.4. 

Among  the  most  conspicuous  landmarks  of  the  sky  is  "the 
Great  Square  of  Pegasus,"  shown  here  and  shown  also  in  Map  II. 
It  is  made  by  three  of  the  brighter  stars  of  Pegasus  in  combination 
with  the  Alpha  (a)  of  Andromeda.  It  is  at  the  east  in  the  evening 
skies  of  August,  is  directly  above  us  in  November,  and  sets  at  the 
west  in  early  February.  The  star  Epsilon  (e),  magnitudes  2.5  and 
8.5,  is  a  double,  but  a  little  difficult.  In  the  neighboring  constella- 
tion of  Pisces  or  The  Fishes,  the  stars  Zeta  (£),  magnitudes  5.5  and 
6.4,  and  Psi  (i//),  magnitudes  5.5  and  5.8,  are  easier  to  divide. 

Starting  at  one  of  the  northern  corners  of  the  Square  of  Pe- 
gasus, from  the  star  Alpha  (a)  of  Andromeda,  let  us  now  follow 
the  line  which  leads  through  the  latter  constellation.  We  shall 
find  here  the  easy  doubles  Pi  (?r),  magnitudes  4.5  and  8;  and  56, 
magnitudes  5.8  and  6.0;  and  at  the  position  indicated  by  the  little 
triangle  near  the  small  star  Nu  (i/)  we  shall  be  able  to  distinguish 
Andromeda's  great  nebula.  Use  your  eye-piece  of  lowest  power, 

19 


for  you  will  want  a  large  field.  Choose  a  night  clear,  but  not 
flooded  by  the  moonlight,  for  you  will  want  the  benefit  of  contrast. 
This  nebula  is  the  largest  of  the  spiral  type,  its  diameter  having 
been  estimated  as  500,000  times  the  distance  between  the  earth 
and  the  sun,  "light  requiring  eight  years  to  travel  across  it."  It  is 
decidedly  oval  in  shape,  brighter  at  its  center  than  at  its  edges. 
In  a  small  instrument  it  is  not  so  impressive  to  a  beginner  as  is  a 
cluster,  like  the  Pleiades ;  but  in  its  own  way,  in  the  far  reaches  of 
its  faint  luminous  glow,  it  is,  to  the  discriminating  observer,  quite 
as  interesting. 


The   Planets 

The  planets  are  of  our  own  family,  and  revolve 
with  our  little  earth  about  the  sun.  They  are  not 
1909  themselves  great  self-luminous  suns,  as  are  the 
"fixed  stars"  we  have  thus  far  studied.  Because  the 
i9ii  planets  are  thus  near,  and  because  they  chiefly  shine 
by  reflected  light,  they  show  an  appreciable  disc,  or 
1913  surface  outline,  within  the  telescope,  though  only 
Venus,  Jupiter  and  Saturn  are  of  special  interest  in 
a  small  instrument.  Mars,  indeed,  is  worth  observ- 
ing,  for  his  ruddy  glow  and  perhaps  one  of  his  more 
conspicuous  markings,  but  the  much-discussed  "canals"  are  for 
larger  glasses.  Saturn,  however,  even  in  a  small  instrument,  is  an 
object  of  surpassing  interest. 

You  can  easily  identify  Saturn  by  the  steadiness  of  its  yellow 
light.  Your  25  x  eye-piece  will  distinctly  show  the  existence  of  the 
ring  formation,  but  you  can  here  use  the  50  x  with  greater  advan- 
tage. With  the  higher  power  you  will  see  the  chief  peculiarity  of 
the  planet  more  clearly,  though  not  on  so  large  a  scale  as  in  our 
little  cut,  and  you  will  also  see  Titan,  the  largest  of  the  nine  satel- 
lites. But  Saturn's  chief  attraction  is  shown  in  our  illustration,  a 
phenomenon  unique — so  far  as  our  knowledge  goes — in  the  whole 
range  of  our  universe.  Because  of  the  changes  in  the  relative  posi- 
tions of  the  planets  in  reference  to  each  other,  the  rings  of  Saturn 
are  sometimes  turned  "edge  on"  toward  the  earth  and  are  then 
difficult  to  see.  This  was  the  case  in  1907,  as  shown  in  the  first 
figure  of  our  little  illustration.  But  through  1909  and  1910  the 
rings  gradually  open  out,  permitting  a  more  satisfactory  telescopic 
view.  They  are  composed  of  "swarms  of  meteors"  in  revolution 
about  the  planet  as  a  center.  The  extreme  diameter  at  the  outer 
edge  is  more  than  172,000  miles. 

20 


Venus,  so  splendidly  beautiful  to  the  unaided  eye,  has  no  satel- 
lite to  interest  us  and  no  marked  peculiarity  of  form.  These  facts, 
together  with  its  excessive  brilliance  in  a  glass,  make  it  a  disap- 
pointing telescopic  object.  Most  interesting,  however,  is  the  ob- 
servation of  the  planet  when  she  assumes  her  crescent  phase,  for 
there  are  periods  of  the  year  when  she  puts  on  this  aspect  of  the 
new  moon.  It  is  an  aspect  of  her  charm  which  will  be  presented 
when  she  shines  at  her  brightest  in  the  west  during  the  evenings 
of  January,  1910,  and  in  the  east  during  the  mornings  of  March 
and  April,  1910. 

Jupiter  and  his  satellites  will  form  a  delightful  and  inexhausti- 
ble source  of  interest  and  pleasure.  Even  with  the  25  x  eye-piece 
four  of  the  eight  moons  are  distinctly  visible  in  our  little  instru- 
ment, and  the  field  of  view  is  so  large  and  so  well  lighted  that  the 
spectacle  is  peculiarly  satisfying.  With  the  50  x  eye-piece  they  are 
brought  out  even  more  vividly ;  and  by  a  good  eye,  under  favorable 
conditions,  the  cloud-belts  across  the  body  of  the  great  planet  may 
be  discerned.  The  movement  of  the  satellites  is  so  rapid,  as  they 
revolve  in  their  orbits,  that  we  can  see  them  change  their  relative 
positions  almost  from  hour  to  hour;  one  night  three  will  be  upon 
one  side  the  planet,  one  upon  the  other;  the  next  night  there  will 
be  two  on  either  side;  and,  yet  again,  as  the  satellites  are  hidden 
by  the  body  of  the  planet,  or  are  eclipsed,  or  are  in  transit  across 
his  huge  disc,  one  or  more  of  them  will  be  wholly  hid  from  view. 

References  to  familiar  sources  of  information  for  the  easy  find- 
ing of  the  planets,  together  with  other  inexpensive  literature  con- 
cerning their  nature  and  their  movements  are  given  in  note  10, 
paragraphs  2  and  4,  p.  38. 


21 


OF   THE 

UNIVERSITY 


Part  II. 


The    Moon 


The  Moon 
Some  Interesting   Lunar   Objects 

The  user  of  our  Prism  Terrestrial  Telescope  will  find  especial 
pleasure  in  the  observation  of  the  moon.  Not  only  does  the  ex- 
cellent definition  of  the  instrument  show  the  lunar  topography  with 
remarkable  clearness  and  fullness  of  detail,  but  the  very  fact  that 
a  terrestrial  telescope  does  not  invert  the  image — as  is  the  case 
with  astronomical  telescopes — is  of  much  satisfaction  to  a  begin- 
ner. Our  halftone  engravings  and  our  miniature  key-map  are  pre- 
sented, therefore,  "right-side-up,"  in  harmony  with  the  view  as 
observed  in  a  terrestrial  instrument  and  in  conformity  with  the 
natural  expectations  of  the  eye. 

As  you  look  at  our  first  photograph  of  the  moon  you  will  see 
that  the  objects  on  its  surface  are  made  distinct  to  us  by  the  lunar 
shadows.  As  the  sunshine  dawns  or  dies  away  over  plains  and 
mountains,  the  objects  near  the  edges  of  the  advancing  or  receding 
light  are  brought  into  sharp  relief.  In  the  direct  illumination  which 
obtains  when  the  moon  is  "full,"  we  can  see  little  detail,  for  shad- 
ows are  then  largely  absent.  Looking  at  each  of  our  photographs 
in  turn,  you  will  now  be  able  at  once  to  understand  why  the  same 
object — such  as  Copernicus,  the  huge  crater-mountain  marked  No. 
28  in  our  key-map — should  present  so  different  an  aspect  at  differ- 
ent times.  These  ceaseless  changes  caused  by  the  different  angles 
at  which  the  sun's  light  strikes  the  surface  make  one  of  the  chief 
fascinations  of  lunar  study. 

But  in  order  to  show  clearly  all  of  the  chief  objects  on  the 
moon  by  the  photographic  process,  we  should  thus  have  to  present 
dozens  of  pictures  instead  of  two.  These  two,  however,  are  enough 
to  explain  the  constant  changes  of  illumination  and  to  illustrate 
the  value  of  our  little  key-map.  Without  the  key-map  and  this 
accompanying  explanation  you  might  possibly  infer  from  the  pho- 
tographs themselves  that  the  objects  lying  outside  the  shadows — in 
the  darkness,  or  in  the  confusion  of  the  direct  light — are  always 
hidden  from  observation.  On  the  contrary,  the  region  of  the  moon 
toward  the  reader's  right,  which  seems  obscured  in  the  moon  at 
nine  and  three-quarter  days  by  the  direct  glare  (the  objects  num- 
bered 1,  2,  3,  4  in  the  key-map)  are  as  clear  when  the  moon  is 
younger  (two  to  four  days  old)  as  is  Copernicus  (No.  28)  in  our 
first  engraving. 

25 


The  Moon  at  Nine  and  Three-quarter  Days 

With  the  moon,  as  with  the  stars,  do  not  assume — as  beginners 
are  so  apt  to  do — that  the  more  powerful  eye-piece  is  necessarily 
the  first  that  should  be  employed.  As  the  lower  powers  always 
afford  a  much  larger  field  of  vision,  it  is  always  well  to  use  the  25  x 
in  locating  the  object  in  the  telescope.  Then  the  50  x  eye-piece 
may  be  substituted.  If  there  is  haze  or  mist,  the  lower  power  may 
well  be  retained;  if  the  atmospheric  conditions  are  good,  you  will 
of  course  gain  with  your  higher  power  a  greater  fullness  of  detail 
and  much  larger  magnification. 

Early  in  our  study  of  the  moon  let  us  mentally  mark  and  note 
the  general  position  of  some  of  the  greater  "seas," — not  seas  in  fact, 
but  dark  plains  upon  the  lunar  surface.  Their  quaint  names  were 
given  them  many  generations  ago.  That  marked  No.  1  was  named 

26 


,fe/\» 

(*K    ) 


"The  Sea  of  Crises,"  or  "The  Sea  of  Conflicts."  We  roughly  trans- 
late the  Latin  titles.  That  marked  No.  5  is  the  Sea  of  Fecundity; 
No.  6  is  the  Sea  of  Nectar;  No.  7  is  the  Sea  of  Tranquility;  No.  8 
is  the  Sea  of  Serenity;  No.  21  is  the  Sea  of  Showers. 

The  Sea  of  Conflicts,  No.  1,  seems  to  be  longer  from  north  to 
south  (up  and  down)  than  from  east  to  west.  This,  however,  is 
an  optical  illusion,  due  to  foreshortening;  its  width,  from  north  to 
south,  being  about  280  miles,  and  the  distance  from  its  eastern  to 
its  western  boundary  being  over  350  miles.  Two  craters  may  be 

readily   discerned  within   it — the   lower 
having  the  name  Picard,  the  upper  be- 
ing called  Peirce.     These  are  so  small 
that  while  they  may  be  readily  seen  with 
the  telescope  when  the  Moon  is  about 
(V?\  four  days  old,  they  are  not  indicated  in 
^      the  key-map.    No.  1  and  its  neighboring 
objects — as  already  stated — are  seen  in 
clear   and  beautiful   detail   in   the   very 
new  moon.    This  great  oval  plain  com- 
prises about  66,000  square  miles.     Just 
Key  Map  above  it,  marked  No.  2  in  the  key-map, 

is  Cleomedes,  a  smaller  formation,  a  walled  plain  78  miles  in 
diameter.  A  little  way  below  No.  1  is  the  crater  Langrenus,  No.  3, 
with  its  terraced  ring  over  9,500  feet  high.  The  next  crater — except 
one  which  we  do  not  mark — is  Petavius,  No.  4,  the  eastern  side  of 
its  great  double  rampart  being  11,000  feet  in  height.  All  these 
objects,  as  has  been  said,  are  too  directly  lighted  to  be  well  seen 
under  the  illumination  of  the  nine  or  ten  day  moon,  so  they  appear 
only  as  bright  patches  in  our  first  photograph. 

In  the  objects  numbered  10,  11,  12  we  again  find  almost 
"drowned  in  light,"  three  peculiarly  interesting  craters  which  in 
the  younger  moon — at  about  six  days  old — are  superbly  clear.  In 
this  particular  case,  however,  we  find  recompense  in  our  second 
photograph.  For,  ten  days  later,  in  the  receding  light  of  the  sun, 
these  objects — Theophilus,  Cyrillus  and  Catharina — are  again  de- 
fined in  the  lines  of  grateful  shadow. 

Theophilus,  No.  10,  is  probably  the  deepest  of  the  moon's 
craters,  the  general  line  of  the  ring  being  from  14,000  to  18,000  feet 
above  the  chasm.  Of  this  triple  group,  it  "first  catches,"  says 
Webb,  "the  rising  sun,  and  I  have  seen  it  far  beyond  the  ter- 
minator (the  shadow  line)  and  even  without  the  telescope,  five 
days  after  new ;  it  is  a  grand  object  when  filled  with  night,  through 
which  its  glittering  central  peak  comes  out  like  a  star."  In  our 

27 


The  Moon  at  Eighteen  and  a  Half  Days 

second  photograph,  in  the  now  retreating  shadows  of  the  sun,  you 
can  clearly  see  the  bright  cap  of  this  central  peak. 

Cyrillus,  No.  11,  is  even  larger;  and  Catharina,  No.  12,  is 
perhaps  the  largest  of  the  three,  irregular  in  character  but  more 
than  16,000  feet  deep.  As  with  all  the  objects  of  our  study  these 
craters  should  be  observed  under  different  illuminations.  If  pos- 
sible, it  is  well  to  make  two  observations  on  the  same  evening — 
one  at  an  early  hour  and  another  somewhat  later.  And  in  using 
the  little  key-map,  each  object  specified  should  be  examined  with 
the  aid  of  both  our  photographs. 

As  our  little  telescope  will  clearly  show  more  than  three  hun- 
dred objects  upon  the  moon's  surface — each  having  its  own  distinct 

28 


and  proper  name — it  is  obviously  impossible  here  to  indicate  them 
all.  And  upon  the  beginner  the  effect  of  so  much  detail  would  be 
confusion  and  discouragement  rather  than  information  and  pleas- 
ure. We  confine  ourselves  to  approximately  forty  objects.  Even 
this  number  will  seem  bewildering  to  the  novice.  We  suggest, 
therefore,  that  for  the  first  few  evenings  of  his  observation  he 
rigorously  confine  himself  to  four  or  five.  Let  him  get  these  well 
in  mind.  Then,  with  these  as  landmarks,  he  will  be  surprised  and 
delighted  to  see  how  rapidly  his  information  will  advance. 

We  have  already  spoken  of  the 
objects  10,  11,  12 — conspicuously 
lighted  in  our  second  photograph  as 
well  as  in  the  six  and  seven-day  moon. 
In  the  nine-day  moon  we  shall  find  an- 
other triple  group  (23,  24,  25  in  the 
key-map)  called  Ptolemy,  Alphonsus, 
and  Arzachel.  This  group  is  shown  in 
both  our  photographs.  Quite  near  the 
edge  of  Alphonsus  you  will  observe 
the  smaller  crater  called  Alpetragius — 

Miniature  Key  Map  Qne    of    the    deepest    On    the    mOOn.       To 

the  right,  No.  26,  is  Albategnius.  One  cannot  but  feel  a  strong 
desire  to  change  some  of  these  formidable  names! 

We  have  hastened  to  speak  of  the  triple  group  23,  24,  25  chiefly 
to  prevent  its  confusion  with  10,  11,  12.  We  will  now  return  to 
some  of  the  earlier  numbers.  In  No.  9  of  our  key-map  we  again 
have  an  object  shown  in  our  photographs  under  two  different  light- 
ings. This  is  Posodonius,  a  walled  plain  about  62  miles  across, 
containing  a  small  but  sometimes  brilliant  crater.  No.  18  is 
Manilius,  and  to  its  right  is  Pliny.  The  former  is  over  7,500  feet 
deep  and  about  25  miles  in  diameter.  No.  13  is  Aristotle,  No.  14 
is  Eudoxus ;  a  superb  pair  of  craters,  the  terraced  wall  of  the  former, 
over  11,000  feet  high,  being  crowned  by  two  turrets  of  15,000  feet. 
In  this  great  cavity,  says  one  authority,  the  Mount  Etna  of  our 
earth  could  stand.  No.  19  is  Cassini,  a  ring-plain  with  a  small 
deep  crater.  No.  20  is  Plato,  well  shown  in  both  our  photographs,  a 
great  ring-plain  60  miles  across.  Above  Plato  lies  the  Sea  of  Cold; 
below  Plato  is  the  Sea  of  Showers,  and  within  the  latter  we  have 
marked  for  special  consideration  the  objects  numbered  15,  16  and 
17,  Archimedes,  Autolycus,  and  Aristillus.  The  range  of  moun- 
tains terminating  at  Eratosthenes  (No.  22)  is  known  as  the  Apen- 
nines, a  chain  somewhat  like  the  mountains  of  the  earth.  Its  length 
is  460  miles.  To  the  left  of  No.  22  lie  the  Carpathian  Mountains, 
and  in  No.  28  we  have  one  of  the  most  superb  of  lunar  spectacles, 

29 


the  huge  crater  Copernicus,  56  miles  in  diameter.  It  is  the  center, 
as  may  be  seen  in  our  second  photograph,  of  one  of  those  systems  of 
light  radiation  which  form  one  of  the  most  striking  features  of  the 
moon's  aspect.  Another  center  of  these  radiations,  as  you  will  see, 
is  Kepler,  No.  36.  No.  27,  Aristarchus,  is  usually  regarded  as  the 
most  brilliant  single  point  upon  the  moon.  No.  34,  Grimaldi,  is  by 
contrast  the  darkest  of  the  lunar  craters. 

In  No.  29,  seen  far  better  in  our  first  photograph  than  in  our 
second,  we  have  Bullialdus,  a  great  crater,  9,000  feet  deep  and  38 
miles  across.  No.  35  is  Rheinholdt.  We  turn  now,  however,  to  the 
southern  or  lower  quarter  of  the  moon's  surface  in  order  that  we 
may  close  our  brief  descriptions  with  a  word  concerning  a  few  of 
the  objects  in  the  neighborhood  of  No.  30,  Tycho,  "the  metropolitan 
crater."  The  whole  region  is  one  of  mighty  cataclysm,  of  appalling 
heights  and  depths.  Longomontanus,  No.  31,  is  apparently  one  of 
the  oldest  of  volcanic  formations,  its  great  walls  having  been  rent 
and  shattered  by  recurrent  explosions.  Maginus,  No.  32,  is  one 
of  a  number  of  lunar  objects  which,  while  presenting  a  superb  spec- 
tacle under  certain  phases  of  illumination,  are  entirely  invisible  at 
full  moon.  Clavius,  No.  33,  is  especially  interesting  by  reason  of 
the  craters  within  its  limits;  their  shadows  are  finely  outlined  in 
the  lunar  sunrise.  This,  and  many  objects  which  must  necessarily 
be  omitted  from  a  list  as  brief  as  the  present  one,  may  be  further 
studied  in  some  of  the  publications  cited  in  par.  10,  p.  38. 

The  great  crater  Tycho,  No.  30,  is  not  only  of  unique  interest 
in  itself,  but  is  the  central  point  for  the  most  splendid  system  of 
radiations  on  the  moon.  In  both  our  photographs  the  reader  can 
partially  see  the  spreading  of  these  lines  of  light.  So  brilliant  do 
they  become  when  the  moon  is  full  that  this  huge  crater  dominates 
the  scene,  the  light-streaks  extending  from  it  in  all  directions. 
Webb  calls  Tycho  "a  most  perfect  specimen  of  the  lunar  volcano, 
roughly  figured  by  Galileo  in  the  earliest  telescopic  representations. 
Its  diameter  is  54  miles,  its  depth  17,000  feet  or  nearly  three  miles, 
so  that  the  summit  of  our  Mont  Blanc  would  drop  beneath  the 
ring.  Its  vicinity  is  thronged  with  hillocks  and  small  craters  so 
that  for  a  long  distance  not  the  smallest  level  spot  can  be  found; 
further  off  the  craters  increase  till  the  whole  surface  of  the  region 
resembles  a  colossal  honeycomb." 


"There  are,"  says  Noble,  in  his  "Hours  With  a  Three-inch 
Telescope,"  "few  more  curious,  instructive,  nay  even  startling 
sights  in  the  heavens  than  the  occultation  of  a  fixed  star,  or 

30 


more  rarely  of  a  planet,  by  the  moon.  When  this  occurs  at  the 
dark  limb  of  our  satellite,  its  suddenness  is  such  as  not  infrequently 
to  extort  an  exclamation  from  the  observer  who  witnesses  it  for 
the  first  time.  .  .  In  describing  her  monthly  path  over  the 
celestial  vault,  it  is  quite  obvious  that  the  moon  must  pass  be- 
tween us  and  such  stars  as  lie  in  her  course ;  the  stars  being — 
for  our  present  purpose — at  an  infinite  distance,  while  she  is  only 
some  239,000  miles  from  us.  .  .  Travelling  thus,  as  I  have  said, 
from  west  to  east,  her  eastern  limb  is,  of  course,  the  leading  one, 
or  that  which  covers,  hides,  or  occults  objects  lying  in  her  path. 
From  new  moon  to  full  moon  this  limb  is  unilluminated,  and  the 
effect  of  the  extremely  sudden  extinction  of  a  star  when  the  dark 
limb  hides  it  is,  as  I  began  by  saying,  of  an  absolutely  startling 
character.  'In  a  moment,  in  the  twinkling  of  an  eye,'  the  star 
which  shone  as  a  brilliant  point  in  the  sky  is  blotted  out;  and  its 
place  seemingly  knows  it  no  more,  until  it  reappears  from  behind 
the  opposite  or  illuminated  edge  of  the  moon.  After  full  moon, 
of  course,  the  eastern  limb  is  illuminated,  so  that  the  disappearance 
takes  place  at  the  bright  edge,  and  the  star  on  its  reappearance 
starts  instantaneously  from  behind  the  dark  limb."  The  more 
interesting  occultations  are  fully  predicted  and  enumerated  in  the 
Whitaker's  almanac  mentioned  in  the  closing  paragraph  of  note  10, 
page  38. 

In  addition  to  the  literature  concerning  the  moon,  as  mentioned 
in  note  10,  page  38,  we  also  refer  to  "The  Moon  in  Modern  Astron- 
omy" by  Philip  Fauth,  with  an  introduction  by  J.  Ellard  Gore, 
F.  R.  A.  S. ;  published  by  the  Van  Nostrand  Co.,  New  York.  With- 
out endorsing,  necessarily,  some  of  the  theoretic  contributions  of 
the  volume  we  are  sure  the  amateur  astronomer  will  find  much 
pleasure  in  its  illustrative  and  descriptive  matter. 


31 


Part  III. 


Notes  and  Suggestions 


Notes  and  Suggestions 

1.  Readers  of  this  booklet  are  advised — before  beginning  the 
specific  use  of  any  particular  part  of  it — to  read  it  through  as  a 
whole.    The  suggestions  made  at  one  point  will  often  prove  helpful 
in  other  connections. 

2.  Our  half-tone  engravings  of  the  moon  are  reduced  from 
direct   contact  prints   of   negatives   made   with   the   great  40-inch 
Yerkes   telescope,    designed   and   constructed   by   The   Warner   & 
Swasey  Company  for  the  University  of  Chicago  at  Williams  Bay, 
Wisconsin.     As  all  photographs  taken  with  an  astronomical  tele- 
scope show  the  object  inverted  in  the  field  of  view,  the  above  prints 
are  presented  "erect"  in  this  booklet,  in  conformity  with  the  re- 
quirements of  a  terrestrial  instrument. 

3.  The  user  of  a  camera  expects  to  make  a  few  failures  before 
getting  the  best  results,  the  user  of  any  form  of  mechanical  equip- 
ment— whether  it  be  the  bicycle,  the  automobile  or  even  a  pair  of 
roller  skates — expects  to  put  a  little  thought  and  care  into  the 
mastery  of  the  machine.     It  is  so  with  a  telescope.     While  far 
simpler  than  the  "modern  creations"  which  we  have  mentioned,  the 
beginner  should  not  begrudge  the  expenditure  of  a  little  thought 
and  time  if  he  would  gain  intelligent  command  of  the  instrument 
itself  and  of  the  resources  which  it  will  bring  him. 

4.  It  is  to  aid  the  beginner  in  one  department  of  its  use  that 
this  booklet  has  been  prepared.     Yet  it  is  not  intended  as  a  library 
on  astronomy  or  as  a  complete  telescopic  manual.    The  little  maps 
are  necessarily  inadequate  and  are  not  presented  as  a  substitute  for 
such  a  "star  atlas"  as  the  advanced  amateur  will  desire.     In  maps 
so  small  many  stars  must  necessarily  be  omitted;  other  and  per- 
haps smaller  stars — because  of  some  special  telescopic  interest,  or 
because  of  their  connection  with  the  constellation  figures — have 
been  included.    The  diagrams  are  offered  just  as  rough  approximate 
guide-maps  for  elementary  telescopic  work. 

5.  While  our  references  to  particular  stars  are  so  clearly  given 
as  not  to  necessitate  the  memorizing  of  the  Greek  alphabet,  that 
alphabet  is  here  printed  as  a  matter  of  convenience  to  the  beginner. 
A   general  familiarity  with  the  characters  is  easily  acquired  and 
indispensable  in  the  use  of  larger  star-maps:     Alpha,  a;  Beta,  /?; 
Gamma,    y;    Delta,    8;    Epsilon,    €;    Zeta,    £;    Eta,    ??;    Theta,    0; 
Iota,  t;  Kappa,  K;  Lambda,  A;  Mu,  /*;  Nu,  v;  Xi,  £;  Omicron,  o; 
Pi,  TT  ;  Rho,  P ;  Sigma,  o- ;  Tau,  r ;  Upsilon,  v ;  Phi,  <f> ;  Chi,  x ;  Psi,  \j/ ; 
Omega,  o>. 

35 


6.  As  already  suggested  on  p.  12,  the  use  of  a  plain  straight- 
back  chair,  without  arms,  will  be  of  much  service  to  the  observer 
employing  so  light  an  instrument.     As  he  takes  his  place  in  the 
chair  the  instrument  may  be  drawn  toward  him,  and — sitting  al- 
most directly  beneath  the  tripod,  a  leg  of  the  tripod  falling  naturally 
into  position  at  each  side  of  him — he  will  be  able  with  very  little 
adjustment  of  the  telescope  to  command  almost  any  altitude.    Stars 
obscured  by  mists  at  the  horizon  or  inconveniently  high  up  may  be 
permitted  to  wait  the  observation  of  those  at  better  range.     If  the 
beginner  will   early  learn  to   take  what   Fortune  brings,   he   will 
always  find  that   Fortune,  whatever  her  negligences,   will  surely 
bring  the  stars  again.     At  a  later  hour  on  the  same  evening,  or  at 
the  same  hour  on  a  later  evening,  he  will  be  rewarded. 

7.  Among  the  interesting  astronomical  phenomena  of   1909- 
1910  is  the  return  of  Halley's  comet,  after  an  absence  of  nearly  76 
years.     The  comet  in  October,  1909,  will  be  not  far  from  the  little 
star  marked  Nu  (v)   in  Orion   (Map  II).     You  will  see  this  star 
just  above  the  bright  star  Betelgeuse,  and  a  little  to  the  left.    Pass- 
ing westward  through   the   constellation   Taurus   the   comet   will 
move  along  the  southern  part  of  the  constellation  Aries,  and  from 
thence — as  we  watch  it  from  week  to  week — we  shall  see  it  pass 
into  the  region  of  Pisces,  the  Fishes.    A  telescope  will  probably  be 
needed  for  its  observation  during  the  autumn  of  1909,  but  by  the 
early  spring  of  1910  it  is  likely  to  be  a  conspicuous  object  even  to 
the  unaided  eye.    Its  visible  advance  into  our  skies  will,  of  course, 
be  first  heralded  by  those  commanding  larger  instruments ;  the  pos- 
sessor of  our  two-inch  terrestrial  will  thereafter  find  much  interest 
in  observing  its  first  appearance  and  its  gradual  brightening  under 
the  modest  powers  of  his  own  telescope. 

8.  Some  one  has  well  said  that  "the  most  important  part  of 
a  telescope  is  the  man  at  the  small  end  of  it."    This  is  but  a  recog- 
nition of  the  fact  that  there  is  such  a  thing  as  a  trained  eye — as  well 
as  a  trained  hand  or  a  trained  will.     The  beginner  may  be  sure, 
therefore,  that  as  he  extends  his  familiarity  with  his  instrument 
and  as  he  gains  in  clearness  and  accuracy  of  vision,  his  telescope 
will  be  an  increasing  satisfaction.     Two  of  the  personal  conditions 
of  good-seeing  may  be  especially  commended:    Work  in  comfort, 
and  work  with  deliberation.     Holding  the  telescope  in  trying  posi- 
tions, getting  the  head  or  body  into  fatiguing  or  unnatural  attitudes, 
are  directly  embarrassing  to  clear,  accurate  seeing.     And  because 
we  thus  see  with  the  mind  as  well  as  with  the  eye,  much  of  the 
reward  of  exquisite  vision  is  found  in  deliberation.     Do  not  rush 
from  star  to  star.     In  looking,  for  example,  at  a  beautiful  double 
star  like  the  Gamma  (y)  in  Andromeda — see  p.  14 — quiet,  thought- 
ful observation,  after  you  have  secured  a  sharp  focus,  will  add  much 
to  your  real  pleasure  in  what  you  see.    In  this  case,  you  are  looking 
at  two  splendid  suns  thousands  of  millions  of  miles  distant  from 
our  earth,  so  different  in  their  chemical  constitution  that  their  con- 
trasted colors  are  at  least  partially  conveyed  to  us  through  all  the 
intervening  space. 

9.  In  our  little  map  at  the  top  of  p.  12  the  Dipper  is  shown 
in  its  approximate  position  for  the  early  evening  of  May  1st.     As 

36 


it  turns  westward  (to  the  observer's  left),  the  two  stars  marked 
"The  Pointers"  (no  matter  what  the  position  of  the  Dipper),  will 
always  indicate  the  direction  of  the  bright  star,  Polaris,  or  the 
Pole  Star,  which  lies  nearest  to  the  polar  "hub."  All  the  stars  in 
our  little  map,  ever  keeping  the  same  permanent  relations  to  each 
other — as  though  fixed  on  the  respective  spokes  of  a  great  wheel — 
revolve  also,  as  does  the  Dipper;  but  Polaris  lies  so  near  the  pole 
of  the  heavens  that  its  motion  is  almost  unappreciable ;  it  seems  to 
the  "wayfaring  man"  to  stand  ever  fixed  at  the  true  north.  It  is 
also,  as  you  can  see,  the  leading  star  in  the  "Little  Dipper,"  part 
of  the  constellation  called  "Ursa  Minor." 

Still  looking  at  our  first  map,  you  will  see  that  the  further  a 
star  is  from  the  pole  the  larger  must  be  the  circle  it  describes,  as 
the  great  wheel  revolves ;  and  that  the  stars  located  further  out  on 
its  spokes  (to  continue  our  figure)  will,  with  the  wheel's  turning, 
dip  below  the  horizon  for  a  shorter  or  longer  period.  Those,  how- 
ever, that  lie  within  about  forty  degrees  of  the  pole  are  never 
carried  quite  out  of  the  sight  of  observers  in  the  latitude  of  Cleve- 
land and  New  York;  they  are  called  the  stars  of  the  "circumpolar 
constellations."  These  are  roughly  indicated  in  Map  I,  and  are 
always  in  our  night  sky. 

The  stars  that  are  further  from  the  pole  are  indicated  in  Maps 
II,  III,  and  IV.  They  pass  out  of  our  night  skies  for  shorter  or 
longer  periods  of  time ;  and  as  we  come  to  study  them  we  shall  see 
that  our  figure  of  speech  must  be  changed.  For,  as  we  look  toward 
the  true  north,  we  are  gazing  not  strictly  at  the  hub  of  a  flat  wheel, 
but  toward  the  pole  of  a  hollow  sphere, — its  apparent  axis  the  pro- 
jection of  the  earth's  axis,  and  its  equator  the  projection  of  our 
own  equator.  We  may  imagine  the  spokes  of  the  revolving  wheel — 
as  they  extend — gradually  bending  inward  toward  us,  and  forming 
the  ribs  of  a  vast  including  globe.  We  stand — enclosed  as  it  were — 
at  the  sphere's  center. 

The  circumpolar  stars  turn  with  the  sphere  itself,  but  as  they 
lie  so  near  its  pole,  the  circle  of  their  revolution  never  carries  them 
below  our  horizon.  Sometimes,  for  example,  we  see  the  Dipper 
above  the  North  Star,  sometimes  below  it;  sometimes  it  is  a  little 
to  our  left,  the  bowl  slowly  turning  downward,  sometimes  it  is 
toward  the  right  with  the  bowl  climbing  upward,  but  it  is  always 
in  our  northern  sky.  Yet,  with  the  sphere's  turning,  the  stars 
further  from  the  pole  (Maps  II,  III,  IV),  like  bright  points  fixed 
on  the  inner  surface  of  its  concave  sides — as  these  arch  themselves 
above  and  below  the  horizon — appear  and  disappear  according  to 
their  hours  and  their  seasons.  A  few  minutes  of  actual  observa- 
tion for  a  couple  of  evenings  will  make  this  subject  clear,  even  to 
children  of  grammar-school  grades.  An  admirable  and  much  fuller 
exposition  of  the  diurnal  motion  of  the  stars  will  be  found  in 
Newcomb's  volume,  mentioned  on  p.  38. 

10.  The  beginner  may  wish  to  supply  himself  with  a  few 
volumes  that  will  help  to  enlarge  his  knowledge.  First,  he  will 
enjoy  gaining  some  measure  of  familiarity  with  the  chief  constella- 
tions. Among  the  best  helps  here  are  Olcott's  "Field  Book  of  the 

37 


Stars,"  published  by  Putnam's,  New  York;  and  Serviss's  "Astron- 
omy with  an  Opera  Glass,"  published  by  D.  Appleton  &  Co.  A 
Planisphere  will  be  found  a  most  useful  device  for  ascertaining  the 
positions  of  the  stars  from  night  to  night.  An  inexpensive  one  is 
sold  by  Thomas  Whittaker,  2  Bible  House,  New  York.  As  a 
substitute,  readers  of  French  may  prefer  to  use  one  upon  the  same 
plan  as  Whittaker's,  called  the  "Carte  Celeste,"  published  by  Burk- 
hardt,  2  Place  du  Molard  a  Geneve,  to  be  had  through  any  of 
Brentano's  book-stores. 

Readers  of  German  will  find  attractive  star  maps  and  ex- 
cellent descriptive  matter  in  the  Stern-Atlas  of  Jacob  Messer.  The 
"Himmel  Atlas"  of  Schurig  is  less  expensive  and  the  new  edition 
is  extremely  useful  even  to  those  who  do  not  read  German.  Both 
volumes  may  be  had  of  G.  Steckert,  129  W.  20th  St.,  New  York. 
Among  English  atlases  may  be  mentioned  "The  New  Star  Atlas," 
by  Proctor,  published  by  Longmans,  Green  &  Co. ;  and  Sir  Robert 
Ball's  "Popular  Guide  to  the  Heavens,"  published  in  New  York 
at  $4.50,  by  Van  Nostrand.  The  latter  contains  not  only  a  star 
atlas,  but  charts  showing  the  position  of  the  stars  from  month 
to  month,  simple  tables  for  finding  the  planets,  photographs  of 
clusters  and  nebulae,  and  admirable  maps  of  the  moon,  etc. 

Among  the  many  interesting  books  upon  the  general  principles 
and  facts  of  astronomy,  we  may  mention  S.  P.  Newcomb's  "Popular 
Astronomy,"  published  by  the  American  Book  Co.  It  is  especially 
clear  and  able  in  its  expositions.  Among  other  admirable  text-books 
may  be  mentioned  those  by  Todd,  Young,  and  Moulton.  Our  little 
cut  of  Saturn  on  p.  20  is  drawn  from  a  portion  of  a  cut  in  Prof. 
Todd's  "New  Astronomy,"  the  American  Book  Co.,  New  York.  In 
the  use  of  the  telescope,  whether  in  observing  the  moon  or  the  stars, 
the  advanced  amateur  will  want  some  such  volume  as  "Webb's 
Celestial  Objects  for  Common  Telescopes,"  2  vols.,  $1.75  each; 
London  and  New  York,  Longmans,  Green  &  Co.  Much  of  it  will 
be  too  advanced  for  the  beginner,  but  even  very  early  in  his  work 
he  will  find  a  great  deal  in  it  to  give  him  pleasure.  Among 
more  popular  books,  Noble's  "Hours  With  a  Three-inch  Telescope" 
(Longmans,  Green  &  Co.)  is  especially  useful  and  interesting  for 
its  chapters  on  the  moon. 

In  following  the  course  of  the  planets  the  beginner  will  find  a 
good  almanac  almost  indispensable.  The  astronomical  matter  pub- 
lished in  the  New  York  Tribune  almanac  and  in  the  almanac  of  the 
Brooklyn  Eagle  usually  presents  a  simple  table  showing  in  which 
constellation  each  planet  may  be  found  from  week  to  week  through- 
out the  year.  The  best  almanac,  however,  for  the  amateur  astron- 
omer is  undoubtedly  the  English  "Whitaker's,"  published  at  12 
Warwick  Lane,  London — not  to  be  confused  with  the  American 
house  publishing  the  planisphere.  This  almanac  may  be  secured 
through  any  large  bookseller.  Its  tables  of  the  interesting  as- 
tronomical phenomena  for  each  month  are  especially  full  and 
valuable ;  and  the  movements  of  the  planets  and  the  configurations 
of  the  satellites  of  Jupiter,  etc.,  are  presented  with  simplicity  and 

38 


clearness.     "Whitakers"  may  be  had  in  several  editions,  ranging 
from  about  30c  to  $1.00  in  cost. 

11.  After  the  beginner  has  become  familiar  with  his  instru- 
ment and  with  the  telescopic  objects  already  mentioned,  he  may 
find  it  interesting  to  try  some  additional  double  stars.     The  follow- 
ing list  is,  of  course,  not  complete,  and  of  the  objects  enumerated 
some  are  easy  and  others  are  more  difficult.     If  you  do  not  succeed 
with  a  specific  star  on  one  evening,  try  it  on  another.     Changes  in 
atmospheric  conditions  are  more  frequent  and  more  important  than 
many  amateurs  realize.     In  Map  I,  try — in  the  constellation  Draco 
— the  star  Psi,  \j/   (mags.  4.9  and  6.0)  ;  and  the  star  Omicron,  o 
(mags.  4.8  and  7.6).     In  Cassiopeia,  try  Iota  i  (mags.  4.8  and  8.1). 
In  Perseus,  note  Eta  (>?),  mags.  3.9  and  8.5.     In  Ursa  Minor,  the 
star  Pi,  -a   (mags.  6.9  and  7.6)  ;  in  Cepheus,  Beta,  /?  (mags.  3.5  and 
8.0).     In  this  constellation,  the  star  Mu,  /x,  while  not  a  double  is 
one  of  the  most  famous  of  the  red  stars — called  by  Herschel  a  "gar- 
net."    In  Map  II,  try  in  Auriga  the  star  14,  mags.  5.1  and  7.2;  in 
Aries  you  will  find  easy  doubles,  both  in  Lambda,  A  (mags.  4.8  and 
8.0);  and  Gamma,  y  (mags.  4.8  and  4.7).     Note  the  Lambda,  A,  in 
Orion  (mags.  3.6  and  5.5).     In  Eridanus,  try  the  stars  marked  6 
(mags.  5.7  and  8.0),  55  (mags.  6.0  and  7.1),  and  32  (mags.  4.8  and 
6.4);  and  in  Cancer,  the  star  Zeta,  £  (mags.  4.8  and  6.5).     In  this 
case  as  well  as  in  a  few  others,  the  star  appearing  as  a  double  in  a 
small  telescope  is  really  a  triple  or  a  multiple  as  viewed  in  a  larger 
instrument.     It  may  also  be  interesting  to  note  two  of  the  im- 
portant "variables"  shown  in  Map  II.     We  have  already  spoken 
of  the  star  in  Perseus  marked  Beta,  /?.     The  regular  variations  in 
the  brilliancy  of  its  light  are  so  remarkable  that  the  Arabs  called 
it  "Algol,"  the  Demon.     At  minimum  it  sinks  to  fourth  magnitude, 
but  it  so  remains  only  about  15  minutes,  when,  within  5y2  hours, 
it  becomes  again  a  second-magnitude  star.     Another  remarkable 
variable  in  our  map  is  Mira,  in  the  constellation  Cetus,  the  Whale. 
Its  "period"  is  longer,  being  over  331  days,  but  it  varies  regularly 
from   absolute   invisibility,   for   the   naked   eye,   to   a   star   of   the 
second  magnitude!     Toward  the  bottom  of  Map  IV,  at  the  right, 
you  will  note  the  Alpha  (a)  and  Beta  (/3)  of  Sagittarius,  the  Archer. 
The  star  /?',  if  you  are  living  far  enough  south  to  command  a  view 
of  it,  is  an  interesting  and  easy  double  (mags.  4.2  and  7.2). 

12.  The  beginner,  in  noting  the  little  table  of  symbols  (Map  I), 
will  see  that  the  smaller  the  value  of  the  numeral  the  higher  the 
magnitude  of  the  star.    A  first  magnitude  star  is  a  very  bright  one, 
an  eighth  magnitude  star  is  a  very  faint  one.     Little  attempt  has 
been  made  in  the  maps  themselves  to  secure  absolute  accuracy  as 
to  these  magnitudes — the  drawings  are  necessarily  too  small  for 
the  varied  use  of  many  different  symbols.     But  in  the  text  of  our 
descriptive  matter  the  magnitudes  of  the  components  of  the  double 
stars  are  given  according  to  the  revised  Harvard  Photometry  for 
1908;  or,  in  the  cases  of  a  few  small  components  not  included  in 
that  list,  according  to  the  "Sternverzeichnis"  of  Ambronn,  Univer- 
sity of  Gottingen,  1907.    The  "magnitude"  of  a  star  has  no  neces- 
sary relation  to  its  actual  size ;  the  term  refers  solely  to  its  apparent 
brightness  as  seen  from  our  earth  itself.     Many  of  the  fainter  stars 

39 


may  be  actually  larger  and  more  luminous  than  those  we  classify  as 
first  magnitudes,  their  apparent  faintness,  in  such  cases,  being  due 
only  to  their  greater  distance. 

13.  This  factor  of  distance  in  the  observation  of  the  stars  is  so 
great  that  it  wholly  transcends  all  our  ordinary  conceptions  of 
space.  Yet  a  lack  of  knowledge  upon  this  point  is  the  occasion — 
among  beginners — of  much  disappointment  in  the  first  using  of  a 
telescope.  Do  not  expect  your  telescope,  however  large  in  size 
or  fine  in  quality,  to  lend  a  large  surface  image  or  a  broad  sensible 
disc  to  any  of  the  "fixed  stars." 

With  the  moon  and  with  the  planets,  as  we  have  seen,  things 
are  slightly  different:  these  are  relatively  very  much  nearer  to  the 
earth.  But  so  remote  are  the  hosts  of  the  stars  proper  (the  very 
nearest  being  over  twenty-five  millions  of  millions  of  miles  distant) 
that  no  telescope,  however  great,  will  ever  make  them  in  the  popu- 
lar sense  any  "bigger."  The  highest  power  usually  provided  with 
our  little  instrument  is  50  diameters.  Let  us  suppose,  however, 
that  we  were  able  to  use  a  telescope  affording  us  a  magnifica- 
tion of  5,000  diameters.  As  such  a  power  would  magnify  all 
the  conditions  of  atmospheric  obscurity  or  disturbance  (as  well 
as  the  star)  there  are  few  of  us  who  could  get  any  satisfaction 
from  it.  But  on  the  assumption  that  we  could  use  it  under 
fine  atmospheric  conditions  what  would  it  mean  to  us?  It  would 
bring  a  star  that  might  be  50,000  million  miles  from  us  to  a  distance 
of  1,000  million  miles!  That  is  not  very  near,  is  it?  But  there  is  no 
star  so  near  as  50,000  million  miles:  nor  any  so  near  as  500,000 
million  miles.  The  very  nearest,  as  we  have  said,  is  25,000,000  mil- 
lion miles  away — and  no  star  even  so  near  as  that  is  visible  to  us 
north  of  our  tropic  latitudes. 

Astronomers,  accordingly,  ignore  the  mile  as  a  unit  of  measure. 
Their  unit  is  the  light-year,  the  distance  traversed  by  light — speed- 
ing at  186,330  miles  a  second — in  a  year  of  time.  Our  North  star, 
for  example,  is  at  a  light  distance  of  40  years — that  is  to  say  the 
light  by  which  the  mariner  may  now  take  his  reckoning  (1909) 
was  started  on  its  way  toward  us  in  1869.  As  you  bear  these  dis- 
tances in  mind  you  will  not  find  fault  with  your  little  telescope  if 
it  does  not  make  a  star  assume  the  proportions  of  a  dinner-plate. 
But  if  you  will  employ  your  instrument  under  some  of  the  simple 
instructions  of  the  preceding  pages,  you  will  find  that  it  will  give 
you  results  even  more  interesting  than  the  mere  enlargement  of 
size. 


40 


Specifications 

Objective — clear  aperture 

Powers — two  eye-pieces 

Length  of  telescope 

Weight  of  telescope 

Weight  of  tripod  and  alt -azimuth  mounting 

Weight,  complete  with  carrying  case 

Dimensions  of  carrying  case 


2  inches 

25  and  50 

.     21^  inches 

2}^  Ibs. 

4  Ibs. 

12  Ibs. 

12x6^x4^  inches 


41 


THE  WARNER  &  SWASEY 

PRISM 

TERRESTRIAL 
TELESCOPE 


The  Warner  &  Swasey  Company 

Cleveland,  Ohio,  U.  S.  A. 


Circular  .4-25—1909 


SPECIFICATIONS 


Objective — clear  aperture  2  inches 

Powers — two  eye-pieces  25  and  50 

Length  of  telescope  21  ^  inches 

Weight  of  telescope  2^  Iks. 

Weight  of  tripod  and  alt-azimuth  mounting  4  Ibs. 

Weight,  complete  with  carrying  case  1  2  Ibs. 

Dimensions  of  carrying  case      -     24x6>4  x4^  inches 


THE  WARNER  &  SWASEY  PRISM 
TERRESTRIAL  TELESCOPE 


T 


'HE  2-inch  Porro  Prism  Tele- 
scope is  designed  expressly  for  use 
as  a  terrestrial  instrument.  Its  large 
field,  high  magnification  and  superior 
construction  represent  the  highest  de- 
velopment in  terrestrial  telescopes.  As  an  example  of 
its  excellence,  it  will  show  clearly  so  delicate  an  object  as 
the  moving  second  hand  of  a  watch  at  a  distance  of  300 
feet.  At  from  five  to  seven  miles,  in  good  atmospheric 
conditions,  it  will  reveal  the  time  of  day  by  the  town 
clock  in  the  old  meeting  house  tower,  while  at  ten  miles 
or  more  what  appeared  as  mere  specks  are  sharply 
brought  out  as  recognizable  objects ;  that  white  dot  is  a 
quarry  of  building  stone,  not  a  house.  In  other  words, 
the  2 5 -power  eyepiece  brings  the  object  apparently  twen- 
ty-five times  nearer  and  the  50-power  eyepiece  fifty 
times  nearer.  Of  course,  atmospheric  conditions  modify 
the  "  seeing."  On  a  clear  day,  with  no  wind,  an  object 
can  be  seen  farther  and  better  than  in  hazy  weather,  but 
under  any  conditions  The  Warner  &  Swasey  Prism  Ter- 
restrial Telescope  enables  the  user  to  see  more  and  better 
and  farther.  It  is  the  ideal  instrument  for  terrestrial  use. 


THE  WARNER  &  SWASEY  PRISM  TERRESTRIAL  TELESCOPE 

Complete  with 

ALT-AZIMUTH  MOUNTING,  FOLDING  TRIPOD 
AND  CARRYING  CASE 


HOME  USE 

CIRCULATION  DEPARTMENT 
MAIN  LIBRARY 

This  book  is  due  on  the  last  date  stamped  below. 
1-month  loans  may  be  renewed  by  calling  642-3405. 
6-month  loans  may  be  recharged  by  bringing  books 

to  Circulation  Desk. 
Renewals  and  recharges  may  be  made  4  days  prior 

to  due  date. 

ALL  BOOKS  ARE  SUBJECT  TO  RECALL  7  DAYS 
AFTER  DATE  CHECKED  OUT. 


JAN 3     74-MM 


LD21-A30m-7,'73 
(R2275S10)476— A-32 


General  Library 

University  of  California 

Berkeley 


